BQ24179: 1-4 LiPO Cell Battery Charger/Power Supply

I need a power supply chip/circuit that has two inputs, 1 being a USB, 2 being a 1-4 cell LiPO battery. The power supply needs to provide 5V at 3A minimum. When the USB is plugging into the circuit it should charge the battery connected and still provide 5V 3A.  I believe that the BQ24179 should be able to do this partially what I am not sure of is whether this device maintains a 5V output regardless of the number of battery cells attached. It appears to me that the chip provides the voltage based on the voltage from the battery. This is acceptable if there is a boost-buck converter that can handle the voltage range and still provide the 5V 3A output.